Iowa DNR seeks input on permit changes for in-construction Marshalltown plant

The Iowa Department of Natural Resources is taking comment until Nov. 17 on a series of air permit changes related to the in-construction Marshalltown power plant and conversion to natural gas of units at the adjacent Sutherland power plant.

Interstate Power and Light (IPL) is building a combined-cycle station at the existing Sutherland site in Marshalltown, Iowa. It consists of two F-Class combustion turbines with heat recovery steam generators (HRSG) and one steam turbine. The Marshalltown Generating Station (MGS) is located approximately three quarters of a mile to the west of the existing IPL Sutherland Generating Station (SGS). The combustion turbines will be designed to utilize pipeline-quality natural gas only.

In addition to the two combustion turbines, three natural gas-fired dew point heaters, a natural gas-fired auxiliary boiler, an emergency diesel fire pump and an emergency diesel generator with two associated diesel storage tanks, circuit breakers, and a cooling tower will also be included as part of the Marshalltown project.

Contingent upon and concurrent with this project, IPL will be converting the existing SGS boilers (Boiler 1 and Boiler 3) and existing SGS combustion turbines to natural gas only and will be decommissioning associated material handling facilities under a separate permitting action.

The changes covered by this new permitting were discovered during the initial construction of the facilities. A new dispersion modeling analysis was performed based on the updated specifications.

A public hearing to receive comments will be held between 5:00 pm and 6:00 pm on Monday, November 16 in room 2 at the Marshalltown public library. 

In other recent news for this project:

  • Interstate Power and Light told the Iowa Utilities Board on Sept. 29 that a gas pipeline lateral to the Marshalltown power plant is structurally complete and should be loaded with first gas in November of this year. The board in November 2013 had approved this 13-mile pipeline project. The lateral will supply natural gas from an interconnection with Northern Border Pipeline Co. in Marshall County, Iowa, to the power plant’s gas yard in Marshall County. The pipeline was designed to deliver up to 171,600 Mcf/day.
  • IPL parent Alliant Energy (NYSE: LNT) about the power plant project in its Aug. 6 quarterly Form 10-Q report: “IPL is currently constructing Marshalltown, an approximate 650 MW natural gas-fired combined-cycle [electricity generating unit]. Construction began in 2014 and is expected to be completed in 2017.”
  • The Iowa Utilities Board on May 28 granted IPL a waiver that allows the utility to move forward with oil-to-gas conversions of three existing units at the Marshalltown site. Each unit has a nameplate capacity of 63 MW. IPL stated it planned to convert the units from fuel oil No. 2 to natural gas in order to comply with requirements from the Iowa Department of Natural Resources related to the permitting of Marshalltown. IPL said the conversion must be completed by the first quarter of 2017 or the units must be retired. The conversion is estimated to cost $39 million. IPL said a complete siting review by the board for a fuel conversion would serve no useful purpose.
About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.